Metal drill



(ModeL).

F. H. RICHARDS.

METAL DRI LL Patented June '30, 1885.

N. PETERS. muaw w. wumn ew. n. a

UNrTnn STATES Tries.

PATENT FRANCIS H. RICHARDS, OF SPRINGFIELD, MASSACHUSETTS, ASSIGNOR TO J. D. COX JR. AND F. F. PRENTISS, BOTH OFOLEVELAND, OHIO.

METAL DRILL.

SPECIFICATION forming part of Letters Patent No. 320,966, dated June 30, 1,885.

Application filed July 26, 1883. (ModeL) To all whom it may concern:

Be it known that I, FRANCIS H. RICHARDS, a citizen of the United States, residing at Springfield, in the county of Hampden and State of Massachusetts, have invented certain new and useful Improvements in Metal Drills and Blanks therefor, of which the following is a specification, reference being had to the accompanying drawings, in which- Figure 1 is an end and side view of a completed drill embodying my improvements. Fig. 2 is an end and side view of my improved drill-blank. Fig. 3 is a sectional view taken near the upper or point end of said blank. Fig. 4 is a diagram illustrating certain features of said blank which are shown in Fig. 3.

Similar letters refer to similar parts in all the views.

This invention relates more particularly to that class of metal drills known as twistdrills, and to blanks therefor, the object being to provide a-blank from which accuratelyformed drills can be more readily manufactured, and a drill made from said blank which shall have increased efficiency and durability. For the attainment of these objects the invention consists in a drill and in ablank therefor having certain novel features of construction hereinafter first described in connection with the drawings and afterward particularly pointed out in the claims.

The blank for my improved drill (see Figs. 2, 3, and 4) consists of a suitable metal cylinder or drill-body, A, having slightly elevated ridges corresponding in number and position to the cutting-edges which it is desired that there shall be in the completed drill. On blanks for drills which have straight grooves the ridges should of course lie parallel to the axis but on those for drills which have spiral grooves said ridges must obviously have a correspondingly spiral form. Since spirallygrooved drills are the kind now almost exclusively used for drilling metals, especially in the manufacture of machinery, I have shown and shall now describe my improvements as applied to a drill of this style having two the more usual numbercutting-edges, first premising, however. that my said improvements are applicable as well to drills having straight grooves, and, as intimated above, having a different number of cutting-edges. In Fig. 4 the ridge is shown as being placed upon the cylinder to show more clearly, by contrast with Fig. 3, the construction of the blank.

Referring, now, to Fig. 3, it will be seen that the peripheral outline of the blank is divided up into two series of major parts, a b d, of which the parts I) and d are respectively subdivided into the minor parts 0 f and h 8 Z, and that not all of these parts have the same radius. Of these parts a l and a partof d, between Z and s, represent arcs of the aforesaid cylinder, while f, a, h, and 8 represent the ridges on said cylinder. The cross-sectional areas Grrepresent the metal to be removed in making the grooves of the drill, and they coincide, as shown, with the major part dof the peripheral outline, which part extends from point e to point i. The greatest diameter of the drill is its diameter through points 66, which points are the cutting-edges. The narrowest major part a, extending from point e to point It, corresponds, substantially, to an arc of a size-circle which passes through points e and is concentric to the cylindrical body of the blank, as shown by a dotted line, Figs. 2 and 3. If part a, which Ishall call the sizesurface, deviates in any degree from that sizecircle, it should have aless radius at it than at e, and it is then said to be backed off or relieved to a very slight extent. In practice, however, this relief, whenever it exists at all, should be so slight as not to be appreciable, except by the aid of fine measuring instruments; and it is not what is usually meant by the term relief as applied to this class of drills. The major parts a and b together form what is technically called the land of the drill, being the entire periphery between the grooves G. Part 'b consists, as above noted, of two minor parts, 0 and f, of which parts a is a circular are forming part of the periphery of the round drill-body A, and

lying within and concentric to the size-circle. The minor part f, extending fromk to m, is a curve which joins said are c and the said sizesurface a, and which also lies within said sizecircle. The exact form of this curve f is not essential, since it is neither a part of the cylinder nor of the size-surface. On the opposite side of the ridge the part sis a curve substantially the same as f, but in a reversed position. I11 practice the form of this curve 8 may be varied at the pleasure of the manufacturer, as it is all removed in the grooving operation. Its length also may include any convenient portion of part (I. In practice, however, it is convenient to make a portion of part d, as Z, to be a continuation of part c, and another portion, as h, to be a continuation of part a. The object of this construction is to avoid the necessity of making the cutting edge e at precisely a given point on the periphery of the blank, as would otherwise be required. It is obvious that in this case any variation in the position of said edge between points r is only changes the width of part a (and incidentally of part 0) without making a bad cutting-edge. What is called the relief or backing-off of the drill begins at k, increases rapidly from k to m, and continues uniform from m to i, be ing the amount of space between parts 0 f and the size-circle. By this construction of the parts a better clearance is obtained, with less metal removed, than when using other forms of relief.

The shank of the drill, P 0, Fig. 2, may be cylindrical, as shown, or of any other desired form. a

It is customary to make the diameter of drills increase slightly from 0 to n, including the parts corresponding to part a, to give the drill a longitudinal relief. I11 drills made from my improved drill-blank this part a may have a radius slightly greater at it than at 0,- but I prefer that said radius should be uniform throughout, as this constitutes one part of my present invention.

If the drill in allparts of its periphery is madegliglrtly conical, the'n'the height of the -aforesaid ridges should"besubstantially the same throughout their length; but if parts 0, Figs. 1 and 2, are truly cylindrical, then said ridges should obviously be highest at n, to preserve the said longitudinal relief of the cutting- .edges of the drill. The object of this improvement in the blank is to facilitate the operation of milling the grooves by permitting the rest or guide, which supports it to the milling cutters, to fit said blank closely on the cylindrical surfaces at all times as it is fed through said rest. With the old eonical blanks this continuous fit tflo'viously could not be obtained, the result being that as the smaller part of the blank passed into the rest it would be crowded by the duller cutter to one side, and thus cause the sharper cutter to mill out the deeper groove, making the drill to that extent onesided. This result is entirely obviated by using blanks embodying this part of my in- .ention. The object of the same improvements in the ompleted drill is to facilitate the frequent opration of sharpening the cutting-lips by peritting the rest or guide, which supports it to the grinding-wheel, to fit said drill closely on the aforesaid cylindrical surfaces at all times as it grows shorter by continued use. With the old kinds of drills, having a longitudinal relief over the entire width of'the land, this continuous fit obviously could not be obtained. As such drills are gradually shortened by repeated sharpenings, they fit their guiding-bushing more and more loosely, so that in the operation of sharpening them by a pointing-machine the cutting-lips are ground more and more irregularly, bringing the point less and less central. For these reasons such drills rapidly become inefficient for making holes of uniform sizes, and before they are nearly used up have to be abandoned for newer tools. This part of my invention remedies these difficulties by furnishing. a drill having a cylindrical surface, whereby it may be held with equal closeness at any time from its completion until its grooved portion is entirely ground away. Thus does my invention promote accuracy of workmanship, and, by increasing their durability, secures a greater economy in the consumption of drills.

In Fig. 13 of the drawings accompanying my application Serial No. 103,850, to which reference may be had, I have shown a bushing, 13, having spiral bearing-surfaces L, adapted to fit the cylindrical surfaces only of my improved drill-blank to hold the same during the grooving and pointing operations, and to fit the same surfaces of my improved drill, to hold this during the operation of sharpening it.

It will be understood that the several curves constituting the peripheral outline in Fig. 3 may be so formed as to merge one into the other without having between them any distinct line of demarkation. This is desirable as tending to reduce the difficulty of the turning and the danger of the hardening operation; also, to add to the beauty of the finished article.

It will also be understood that metal bars having incipient drill-grooves formed in them may be used for making my improved drillblank without departing from the spirit of my invention.

I claim as my invention-- 1. As a new article of manufacture, the improved drillblank herein described, consisting in a round drill-body having ridges thereon which correspond, substantially as described, to the cutting-edges to be made in a drill, substantially as described.

2. As a new article of manufacture, the improved drill-blank herein described, consisting in a cylindrical drill-body having ridges which are higher at the point than toward the shank of the drill, substantially as described, and for the purpose specified.

3. .As a new article of manufacture, the improved relieved drill-blank herein described, consisting in a round drill-body having spiral ridges thereon which correspond, substantially as described, to the cutting edges to be made in a twist-drill, substantially as described, and for the purpose specified.

4. As a new article of manufacture, the improved relieved drill-blank herein described, consisting in a cylindrical drill-body having spiral ridges thereon which are higher at the point than toward the shank of the drill, substantially as described, and for the purpose specified.

5. As a new article of manufacture, the improved drill herein described, consisting of a cylindrical drill-body grooved substantially as described, said body being without longitudinal relief, and being provided with elevated cuttingedges at one side of the lands,

FRANCIS H. RICHARDS.

Witnesses:

CHARLES O. PALMER, GEO. G. PRENTIOE. 

